25 June 2025, Volume 20 Issue 3

    

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  Upregulation of EphA2 expression in Chlamydia trachomatis L2 infection and construction and functional validation of its targeted bivalent antibodies

  Journal of Microbes and Infections. 2025, 20(3): 129-138.

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  Chlamydia trachomatis (CT) is a Gram-negative, obligate intracellular parasite that can infect mucosal epithelial cells such as the urethra, vagina, and nasopharynx, as well as the conjunctiva, causing diseases such as trachoma, urethritis, cervicitis, and neonatal conjunctivitis. Among them, L2 CT can cause sexually transmitted lymphogranuloma, which is more invasive than other serotypes and requires long-term treatment, receiving widespread attention. Research has shown that the production of erythropoietin producing hepatocyte receptor A2 (EphA2) on the cell surface can mediate the adhesion and invasion of CT L2, and interfering with their interaction can significantly reduce the infection of CT L2. This study conducted bioinformatics analysis on human cervical epithelial cells infected with CT L2 and found that EphA2 expression was significantly upregulated in the infected group. This study successfully constructed, expressed, and purified a bivalent antibody targeting EphA2, named as EphA2-scFv-Fc. Through ELISA experiments, it was confirmed that there is a dose-dependent specific binding between EphA2-scFv-Fc and EphA2 receptors on the surface of CT L2 susceptible cells HUVEC. This study not only revealed the crucial role of EphA2 in the process of CT infection, but also successfully developed bivalent antibodies that can specifically target EphA2, providing an important foundation for the treatment of CT L2 infection.
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  Research on the Construction of a SARS-CoV-2 Pseudovirus Library Based on the VSV Vector and the Screening of Immune Escape Strains

  Journal of Microbes and Infections. 2025, 20(3): 139-149.

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  This study aims to construct a pseudovirus mutation library of the SARS-CoV-2 spike (S) protein based on the vesicular stomatitis virus (VSV) vector system, in order to screen potential immune escape variants and identify critical mutation sites, thereby providing scientific evidence for vaccine development and epidemic prevention and control. A random mutagenesis kit was employed to introduce random mutations into the receptor-binding domain (RBD) of the Wuhan strain S protein, followed by the construction of a pseudovirus plasmid library and subsequent virus rescue using the VSV vector system. Immune escape variants were screened through serum pressure and limited dilution methods, with their mutation sites validated by sequencing. Results demonstrated the successful construction of the SARS-CoV-2 pseudovirus plasmid library, achieving a positive rate of 98%. Immune escape variants carrying single mutations such as E484K, F486I, G339S, and S477R, as well as double mutations including E484K+K444Q and E484K+K462R, were identified. Some escape variants exhibited significant resistance to neutralizing sera, with a marked reduction in neutralizing titers observed for the E484K single mutant and E484K-related double mutants. This study confirms the feasibility of screening immune escape variants through the construction of a SARS-CoV-2 pseudovirus mutation library and elucidates their potential escape mechanisms and epidemic characteristics. These findings provide important insights into understanding the evolutionary trends of SARS-CoV-2 and offer scientific support for optimizing vaccine development and epidemic prevention strategies.
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  Analysis of serotype distribution and drug resistance of nontyphoidal salmonellosis infection in children in Tangshan City from 2022 to 2024

  XIONG Xueyi, CAO Jinming, LI Juan, YANG Pengwei, HAN Chenxi, YANG Shuo

  Journal of Microbes and Infections. 2025, 20(3): 150-155.

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  Objective To discuss the serotype distribution and drug resistance of nontyphoidal salmonellosis (NTS) infection in children in Tangshan City from 2022 to 2024. Methods: From January 2022 to December 2024, 235 children diagnosed with NTS infection in our hospital were served as subjects. The basic characteristics of the children were statistically explored, and the cultured NTS were subjected to serotype and drug sensitivity tests to analyze the drug resistance of NTS detected in different years. Results In 2022, 2023, and 2024, 79, 84, and 72 cases of NTS infection were detected in the Tangshan area, respectively, with no conspicuous difference in the proportions of male and female cases (P>0.05). Among 235 children with NTS infection, those < 1 year old accounted for the highest proportion (45.53%), while those aged 1-2 years (excluding 2 years) accounted for 29.79%. From 2022 to 2024, the NTS infection rate among children in the Tangshan area was highest in summer and lowest in winter. The serotype test showed that a total of 17 serotypes were detected in 235 children with NTS infection, of which 51.91% were Salmonella typhimurium and 15.32% were Salmonella enteritis. The drug sensitivity test revealed that 235 NTS strains had the highest resistance rate to ampicillin (average value was 77.02%), a relatively high resistance rate to compound sulfamethoxazole (average value was 48.09%), and a relatively low resistance rate to antibiotics such as ceftriaxone (average value was 16.60%) and ceftazidime (average value was 22.55%). There was no conspicuous difference (P>0.05) in the resistance rates of Salmonella typhimurium and Salmonella enteritis to eight antibiotics, including ampicillin. Conclusion: The serotypes of NTS infected children in Tangshan city are mainly Salmonella typhimurium and Salmonella enteritis. NTS strains have a high resistance rate to ampicillin and compound sulfamethoxazole. In clinical practice, antibiotics should be selected reasonably based on the serotype and resistance of NTS infected children to avoid overuse of antibiotics.
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  Comparative study on high-throughput sequencing and culturomics analysis of vaginal microbiota

  Journal of Microbes and Infections. 2025, 20(3): 156-165.

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  【Abstract】 Objective: By using high-throughput culture and high-throughput sequencing to detect the composition of vaginal microbiota in healthy women and patients with bacterial vaginosis, compare the differences in detection results between the two methods to provide evidence for the role of culturomics in vaginal microecology research and clinical disease diagnosis and treatment. Method: Collect vaginal secretions from 10 healthy women and 10 women with bacterial vaginosis, and use 7 different culture media for high-throughput culture of vaginal secretions. Use Clin-ToF time-of-flight mass spectrometry for identification. Simultaneously, high-throughput sequencing of the 16S rRNA V1V2 variable domain was performed directly on all samples. Result: 1. After culturing 20 vaginal secretion samples using culture omics, 35 bacterial genera were identified, with 98 bacterial species at the species level. A total of 17 Lactobacilli were cultured in all samples, of which 9 were detected in both groups. The top three detected strains in the healthy group were Lactobacillus crispatus, Lactobacillus jensenii, and Lactobacillus iners. And in the 5 samples, both Lactobacillus crispatus and Lactobacillus jensenii were cultured simultaneously. The top three detected in the BV group were Lactobacillus iners, Lactobacillus jensenii, and Lactobacillus psittaci. 2. Using the V1V2 domain of the 16S rRNA gene, high-throughput sequencing was performed on the 20 vaginal microbial samples mentioned above, a total of 18 genera were detected in all samples, of which Lactobacillus genus was detectable in all samples, and the relative abundance of Lactobacillus genus exceeded 50% in 12 samples. 3. Among the 20 vaginal microbiota samples, only 9 bacterial genera were identified simultaneously through culture and high-throughput sequencing. Conclusion: By using high-throughput culturomics and high-throughput sequencing methods to simultaneously detect the vaginal microbiota of all samples, the results showed significant differences. High throughput culture has a higher detection rate of bacterial genera and species, and can cultivate lactobacilli with low or undetectable high-throughput sequencing content. Therefore, the use of high-throughput culture groups will have higher application value in the diagnosis and treatment of bacterial vaginosis and the study of vaginal microbiota.
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  Effects of different probiotic treatments on intestinal microecology and immune function of neonates with antibiotic-associated diarrhea

  Journal of Microbes and Infections. 2025, 20(3): 166-172.

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  Objective To analyze the effects of different probiotic treatments on intestinal microecology and immune function of neonates with antibiotic-associated diarrhea. Methods 80 neonates with antibiotic-associated diarrhea treated in our hospital between January 2022 and January 2024 were collected as study subjects. It was divided into an observation group and a control group of 40 cases each according to the method of treatment. The observation group was treated with Clostridium typhimurium two-live bacterial powder, and the control group was treated with Bifidobacterium bifidum three-live bacterial powder. Compare the treatment effect, intestinal flora and immune function changes of the two groups. Results There was no difference in the comparison of gender, age, weight, vomiting, fever and the time from the start of antibiotics to the appearance of diarrhea between the two groups of children (P>0.05). The observation group had a higher overall effective rate than the control group (P<0.05). There was no difference in the counts of Lactobacillus, Lactobacillus, Bifidobacterium, and Eubacterium before treatment between the two groups (P>0.05). The counts of lactobacilli, lactobacilli, bifidobacteria, and eubacteria increased in both groups after treatment, and they were higher in the observation group than in the control group (P<0.05). There was no difference in IgA, IgG and IgM before treatment between the two groups (P>0.05). The IgA, IgG, and IgM of the children in both groups increased after treatment, and the observation group was better than the control group (P<0.05). Conclusion Different probiotics have good effect in treating newborns with antibiotic-associated diarrhea, among which Clostridium typhimurium diphtheriae has the most obvious effect on the intestinal microecology and immune function of the children.
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  The role of neutrophils in arbovirus infections

  Journal of Microbes and Infections. 2025, 20(3): 173-181.

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  Arboviruses are transmitted by blood-sucking arthropods and infect vertebrates through insect bites. Its global prevalence and recurrence threaten human life and health. However, the pathogenic mechanism has not yet been fully elucidated. Neutrophils, as the most numerous leukocytes in the body, are the first to arrive at the site of infection after pathogen invasion, and play a role in the immune response through a variety of anti-infective mechanisms, including phagocytosis of pathogens, production of cytokines and antimicrobial substances, respiratory outbreaks, and secretion of NETs, which is an important member of the body's defence against pathogenic microorganisms. However, it is worth noting that excessive activation of neutrophils may also lead to a strong inflammatory response, which not only fails to control the infection effectively, but also causes damage to host tissues and further aggravates the severity of the infection. Previous knowledge of the role of neutrophils was mostly limited to fighting bacterial and fungal infections. However, it is only in recent years that their role in antivirus has been gradually revealed and valued. Therefore, its role and mechanism in controlling arboviral infections are not yet clear. In this paper, we present an overview of the role of neutrophils in arboviral infections and their possible effects on the host.
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  The mechanism of action of fucoidan in antagonizing Helicobacter pylori infection and regulating gut microbiota

  Journal of Microbes and Infections. 2025, 20(3): 182-192.

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  Helicobacter pylori (Hp), as a common gastric pathogen, has a high global infection rate and is the main cause of various gastrointestinal diseases such as gastritis, gastric ulcers, and gastric cancer. The treatment of eradicating Hp infection NOt only improves the diseases related to gastric inflammation and intestinal microbiota disorders caused by it, but also reduces the risk of gastric cancer. However, with the widespread use of antibiotics, the resistance of Hp continues to rise, increasing the failure rate of treatment. Therefore, there is an urgent need to find new treatment options or adjuvant drugs. Fucoidan has attracted much attention due to its unique biological functions and wide application fields. Research has found that Fucoidan has therapeutic and preventive effects on Hp infection related gastritis and intestinal microbiota disorders. This article elaborates on the main role and related mechanisms of Fucoidan in antagonizing Hp infection, including direct inhibition, reduction of inflammatory response, enhancement of antioxidant capacity, and regulation of gut microbiota. It provides a theoretical basis for Fucoidan to become an effective drug for treating Hp infection and aims to incorporate it into the treatment plan for eradicating Hp infection.